The present invention relates to semiconductor technology, and more particularly to a semiconductor device and method of manufacturing the same.
In semiconductor technology, a semiconductor capacitor is one of the key components of an integrated circuit device. A metal-oxide-metal (MOM) capacitor has many advantages due its compatibility with a copper interconnect structure to achieve a high-density capacitor, thus, it has been widely used in semiconductor devices. For example, conventional CMOS image sensors (CIS) utilize MOM capacitor structures.
FIG. 1A is a cross-sectional view illustrating a relevant portion of a semiconductor device in the prior art. The portion of the semiconductor device includes a substrate 100, a shallow trench isolation (STI) 102 in substrate 100, and a MOM capacitor 106 disposed over the STI 102. MOM capacitor 106 includes multiple comb-shaped metal layers stacked on top of each other, such as a first metal layer Ml, metal layer M2, and a third metal layer M3. An intermetallic dielectric layer is interposed between first, second, and third metal layers Ml, M2, and M3. The portion of the semiconductor device further includes a p-well 101 disposed below STI 102. P-well 101 is located within the periphery of a p+ion implanted region 103 that is connected to first metal layer M1 through a contact hole 105 disposed in an interlayer dielectric layer (ILD) 104.
The above-described structure of the prior art generally has the following problems: when semiconductor substrate 100 is a p-type substrate, noise coming from the semiconductor substrate greatly affects the MOM capacitor and the capacitor formed between the metal layers and the p-well. FIG. 1B is a cross-sectional view illustrating the principles of the effect of noise from substrate 100. When semiconductor substrate 100 is a p-type substrate, noise may be propagating from semiconductor substrate 100 along p-well 101, p+ ion-implanted region 103, contact hole 105 to first metal layer M1, as indicated by the arrow shown in FIG. 1B. Thus, noise from semiconductor substrate 100 may be propagated to the MOM capacitor, first metal layer M1, and other capacitors connected with first metal layer M1. In practical applications, noise from the semiconductor substrate may adversely affect the MOM capacitor. When a semiconductor device includes other components such s a logic circuit, noise from the semiconductor substrate may also adversely affects the components. For example, in a logic circuit of a CMOS image sensor including the above-described MOM structure, noise from the p-type semiconductor substrate may cause flicker noise, fixed pattern noise and temporal noise, adversely affecting the performance of the CMOS image sensor.
Therefore, noise from the semiconductor device may adversely affect the performance of the above-described structure of the prior art. A novel structure and method of manufacturing the same is thus needed to solve the above problems.